Catechol sensor using poly(aniline-co-o-aminophenol) as an electron transfer mediator

In this work, poly(aniline-co-o-aminophenol) (copolymer) was used as an electron transfer mediator in the electrochemical oxidation of catechol due to its reversible redox over a wide range of pH. The experimental results indicate that the anodic peak potential of catechol at the copolymer electrode is lower than that at the platinum electrode in a solution consisting of catechol and sodium sulfate with pH 5.0, and the activation energy for the electrochemical oxidation of catechol at the copolymer electrode is low (23.6 kJ mol−1). These are strong evidence for the electrocatalytic oxidation of catechol at the copolymer electrode. The −OH group on the copolymer chain plays an important role in the electron transfer between the copolymer electrode and catechol in the solution. Based on the catalytic oxidation, the copolymer is used as a sensor to determine the concentration of catechol. The response current of the sensor depends on the concentration of catechol, pH, applied potential and temperature. At 0.55 V (versus saturated calomel reference electrode (SCE)) and pH 5.0, the sensor has a fast response (about 10 s) to catechol and good operational stability. The sensor shows a linear response range between 5 and 80 μM catechol with a correlation coefficient of 0.997. It was found that phenol and resorcinol cannot be oxidized at the copolymer electrode at potentials ≤0.55 V, so controlling the sensor potential affords a good way of avoiding the effect of phenol and resorcinol on the determination of catechol.